Nanako is a young girl who unexpectedly gains supernatural powers while simultaneously losing her memories of the past. Marlow, a scientific genius, happens to be present by chance when she acquires these abilities. Marlow is a hardworking high school student with extraordinary ambitions. He persuades Nanako to join his detective agency by promising to assist her in recovering her memory. Nanako naively trusts him, but Marlow's true intention is to exploit her powers for the benefit of his agency and himself. The narrative progresses as Nanako faces a variety of dangerous missions and mysterious events, yet her naturally cheerful disposition helps her navigate each incident as she resolves one mystery after another.